Referring to FIG. 11, a conventional one-way wrench 80 includes a head 81 defining a circular space 82, a crescent space 83 communicated with the circular space 82 and a hole 86 communicated with the crescent space 83, an annular gear 84 rotationally put in the circular space 82, a pawl 85 movably put in the crescent space 83 for releasable engagement with the annular gear 84 and a spring 87 including an end put in the hole 86 and an opposite end connected with the pawl 85. The spring 87 is compressed between a wall of the crescent space 83 and the pawl 85 for biasing the pawl 85 into engagement with the annular gear 84. The spring 87 is essential for adequate operation of the pawl 85 and hence the entire one-way wrench 80. However, the spring 87 is vulnerable to excessive deformation. Therefore, adequate operation of the one-way wrench 80 could be jeopardized.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.